Fastener driving tool



March 16, 1965 R. H. DOYLE ETAL FASTENER DRIVING TOOL C5 Sheets-Sheet 1 Filed Nov. 29, 1963 AA/D ABM/M F/EDL E2 41- TORA/EYS 7 7w, Mmw fzMw/zomd MM 'March 16, 1965 R. H. DOYLE ETAL FASTENER DRIVING TOOL Filed Nov. 29, 1963 3 Sheets-Sheet 2 IeICh AED H. DOYLE 4M0 AeM/A/ F/EDLEE March 16, .1 R. H. DOYLE ETAL FASTENER DRIVING TOOL 3 Sheets-Sheet 3 Filed NOV. 29, 1963 //\/l/EA/TOE5 Fla/A120 H DOYLE AND ABM/Al F/EDLEZ 6 777m, 4614mm (dim mm Wyn Arm/2M5 Y5.

NNN 3N Unit d St Patent 3,173,340 FASTENER DRIVING TOOL Richard Henry Doyle, Mount Prospect, and Armin Fiedler, Chicago, Ill., assig'nors to Fastener Corporation, Franklin Park, Ill., a corporation of Illinois Filed Nov. 29, 1963, Ser. No. 326,912 Claims. (Cl. 91398) This invention relates to a fastener driving apparatus and, more particularly toa fastener driving apparatus including new and improved pneumatic piston return means.

The use of a compression spring to return the piston in a pneumatic fastener driving tool to its normal position at the end of a power stroke has largely been supplanted by pneumatic piston return means. These pneumatic piston return systems, which can avoid the failures in prior tools resulting from the fatigue of the return spring and also permit a reduction in the height or size of the tool, commonly used in such techniques as continuously supplying the pressure fluid to a differential piston or selectively applying compressed air below the piston following the termination of the power stroke. Some of these types of return systems suffer from the disadvantage that' they reduce the drive power of the tool, and others of thesystems consume an excessive amount of the pressurized fluid and require somewhat complicated valve arrangements for controlling the flow of the piston return fluid. A piston return system that obviates many of these deficiencies is shown and described in the copending application of Richard H. Doyle, Serial No. 246,608, filed December 21, 1962. In this application, the piston return system is shown in conjunction with a pneumatically actuated fastener driving tool including a shiftable or movably mounted cylinder construction, and it would be desirable to embody this return means in a variety of different types of tools. I

Accordingly, one object of the present invention is to provide a new and improved pneumatically actuated fastener driving tool. V

Another object is to provide a fastener driving apparatus including new and improved means for pneumatically returning a piston. Another object isto provide a fastener driving tool including new and improved means for selectively controlling the connection of a pressurized fluid or the atmosphere to the lower end of a cylinder to provide fluid means for returning a drive piston.

A further object is to provide a fastener driving apparatus including fluid operated valve means for connecting the lower end of a drive cylinder to the atmosphere or to a source of fluidfor returning a drive piston atthe end of a piston stroke.

Another object is to provide a fastener driving apparatus including a cylinder to receive fluid expelled from the cylinder during the driving. stroke of a piston, which apparatus also includes means for selectively supplying fluid to the cavity from a reservoir to return the piston to its normal position.

In accordance with these and many other objects, an embodiment of the invention comprises a pneumatically actuated fastener driving tool or apparatus having a housing with a forward head portion and a rearwardly extending hollow handle forming a compressed air or fluid reservoir. The head portion includes a generally vertically extending cylinder having an open upper end and communicating at its lower end with a cavity. A passageway in the housing communicating with theopen upper end of the cylinder includes a first port opening to the atmosphere" and a second port communicating with the reservoir. A manually controlled valve normally connects the passageway to the atmosphere through one port and is operable to a position in which the connection to the atmosphere is closed and the passageway is connected to the reservoir through the other port to supply compressed air to the cylinder. This air drives a piston which is slidably mounted in the cylinder and which is connected to a fastener driving blade downwardly from a normal position adjacent its open upper to a lower position. During this power stroke of the piston, the air disposed in the cylinder below the piston is discharged.

The drive piston is selectively returned to its normal position under the control of valve means provided in a passageway communicating with the cavity. In the setting to which this valve is operated during the driving stroke of the piston, the passageway is connected to the atmosphere to permit the air discharged into the cavity from the lower end of the cylinder to be exhausted to the atmosphere so that the downward movement of the piston is not damped or impeded by a confined cushion of air. In the other setting of this control valve the connection between the passageway and the atmosphere is closed off and this passageway is connected to the reservoir to supply compressed air or pressurized fluid to the lower end of the cylinder for returning the piston to its normal position adjacent the open end of the cylinder. This valve means is operated to its second position to establish the flow of the piston return air from the rcser: voir to the lower end of the cylinder under the control of a fluid means responsive to the pressure within the upper end of the cylinder. This fluid means operates the valve means to its second position whenever the piston is not in its normal position and the manually controlled valve is in a setting connecting the upper end of the cylinder to the atmosphere. In one embodiment, the piston return control valve comprises a single valve assembly controlled by the fluid operating means responsive to the pressureat the open upper end of the cylinder. In another embodiment, separate valves for connecting the cavity to the atmosphere and to the reservoir are provided. In this embodiment, fluid operated means responsive to the pressure at the open end of the cylinder controls the valve for supplying compressed air tothe lower end of the cylinder, and the separate valve means for connecting the lower end of the cylinder to the atmosphere is directly responsive to the setting of the manual control valve.

Many other objects and advantages of the present invention will become apparent from considering the following detailed description in conjunction with the drawings, in which: I

FIG. 1 is a fragmentary top elevational view of a fastener driving tool embodying the present invention;

FIG. 2 is a fragmentary sectional view taken along line 22 in FIG. 1 illustrating a fastener driving tool in a normal condition; v

FIG. 3 is an enlarged fragmentary sectional view taken along line 33 in FIG. 1 illustrating the tool and an exhaust valve for the lower end of a cylinder in the tool in a normal condition;

FIG. 4 is an enlarged fragmentary sectional view taken along line 44 in FIG. 1 illustrating the tool and a p ston return valve for supplying fluid to the lower end of the cylinder in a normal condition;

FIG. 5 is an enlarged fragmentary sectional view taken along line 5-5 in FIG. 1 illustrating the piston return valve in a normal condition and the exhaust valve in ari operated condition during a power stroke of the tool;

FIG. 6 is an enlarged fragmentary sectional view simi' lar to FIG. 5 illustrating the tool at the conclusion of the power stroke and at the beginning of a piston return stroke with the piston return valve operated and the exhaust valve released;

FIG. 7 is a fragmentary sectional View of a second em bodiment of a fastener driving tool embodying the present invention shown in a normal condition; and

FIG. 8 is a fragmentary view similar to FIG. 7 illustrating the fastener driving tool following the termination of a power stroke and at the beginning of a piston return stroke.

Referring now more specifically to FIGS. 1-6 of the drawings, therein is illustrated a fastener driving tool which is indicated generally as 10 and which embodies the present invention. The tool 10 includes a housing 12 having a forward and generally vertically extending head portion 12a and a rearwardly extending hollow handle portion 12b forming a reservoir 14 to which a pressurized fluid, such as compressed air, is supplied in any suitable manner, as by flexible air line. The head portion 12a of the housing 12 includes a cavity 16 in which is mounted a cylinder 18 having its lower end in communication with the cavity 16 and an open upper end in continuous communication with a passageway 20 formed in the housing. A manually actuated control valve assembly indicated generally as 22 normally connects the passageway 20 to the atmosphere through a passageway 24 formed in the hollow handle portion 12b and is operable to a position in which it connects the passageway 20 to the fluid in the reservoir 14. The fluid admitted to the passageway 20 enters the open upper end of the cylinder 18 and drives a piston 26 which is slidably mounted within the cylinder 18 and which is secured to the upper end of a fastener driving blade 28 downwardly so that the lower end of the driver blade 28 engages and drives a fastener 30 supplied to a drive track 32 in a nosepiece assembly 34 by a magazine assembly indicated generally as 36.

During the downward movement of the piston 26, the air disposed within the cylinder 18 below the piston 26 is discharged to the atmosphere through the lower end of the cylinder 18 under the control of an exhaust valve assembly indicated generally as 38 (FIG. 3) which is operated to an open condition in direct response to the admission of pressurized fluid to the passageway 20. When the piston 26 is to be pneumatically returned to its normal position, the control valve assembly 22 is released so that the passageway 20 is again connected to the atmosphere and the exhaust valve assembly 38 is restored to its normal condition in which communication between the cavity 16 and the atmosphere is closed. When the compressed air disposed in the cylinder 18 above the piston 26 is exhausted to the valve assembly 22 through the passageway 24, a piston return valve assembly indicated generally as 40 (FIG. 4) is operated to connect the cavity 16 directly to the reservoir 14. The pressurized fluid supplied by the reservoir 14 acts on the lower surface of the piston 26 to return this piston from its displaced position adjacent the lower end of the cylinder 16 to a normal position adjacent the open upper end thereof. When the piston 26 reaches its normal position, the piston return control valve assembly 40 is automatically operated to close the passageway between the cavity 16 and the reservoir 14 and returns the tool 10 to its normal condition.

The mechanical construction of the housing 12 and the magazine assembly 36 is disclosed in detail in a contemporaneously filed application of Thomas H. Dorney, Serial No. 326,913, filed the same day. In general, the head portion 12a of the housing 12 includes a structure defining a circular opening 42 in which a flanged portion 18a of the cylinder is received with the interface between the wall of the head portion 12a and the outer wall of the flanged portion 18a being sealed by a pair of resilient O-rings 44. An upper opening in the. head portion 12a is closed by a closure cap 46 secured to the housing 12 by a plurality of machine screws 48 with a resilient sealing gasket 49 interposed therebetween. An opening 50 in a depending portion 46a on the closure cap 46 carries a block or bumper 52 of resilient material that engages the upper end of the piston 26, and an annular resilient bumper 54 is disposed in the lower end of the cavity 16 to cushion the termination of the power stroke of the piston 26. The bumper 5,4 is held in position at the bottom of the cylinder 18 by engagement with a shouldered portion 18b formed on the cylinder 18. The lower end of the interior of the cylinder 18 is placed in communication with the cavity 16 through a plurality of peripherally spaced openings 56. The interface between the outer wall of the piston 26 and the inner wall of the cylinder 18 is sealed by a pair of spaced resilient O-rings 58 and 60 carried on the piston.

The connection of the open upper end of the cylinder 18 to either the atmosphere or the fiuid reservoir 14 is controlled by the manually actuated control valve assembly 22. The assembly 22 includes an exhaust valve seat 62 carried on the housing 12 and having a downwardly and inwardly tapered opening 64 through which the passageway 20 is normally placed in communication with the exhaust passageway 24. The opening 64 can be closed by a resilient O-ring 66 carried on the upper end of a valve stem 68. A resilient valve element 70 is also carried on the valve stem 68 disposed between a shouldered portion 68a on the valve stem 68 and a piston 72 that is secured to the lower end of the stem 68. The resilient valve element 70 normally closes a port or passageway 74 interposed between the reservoir 14 and the passageway 20. The piston 72 carries an O-ring 76 and is slidably mounted within a cylinder 78 formed in a valve body 80 that is threadedly received within a tapped opening 82 in the housing 12.

A pilot valve assembly is included in the control valve assembly 22 to control the operation thereof and to permit the assembly 22 to be operated with a minimum manually applied force. This pilot valve assembly includes an operating pin 84 that is slidably mounted within an axial bore formed in a member 86 that is threadedly received within an opening 88 in the valve body 80. An O-ring 90 seals the interface between the valve body 80 and the member 86. The upper end of the operating pin 84 is tapered and carries an O-ring 92 that operates as a valve element to control communication between the reservoir 14 and the bore or opening 88 through a passageway 94. In the normal condition or released state of the control valve assembly 22, compressed air flows from the reservoir 14 through the passageway 94 to deflect or distort the O-ring 92 to permit the compressed air to build up within the upper end of the opening 88. This compressed air flows through a passageway 96 in the valve body 80 to enter the lower end of the cylinder 78. This compressed air, which is at the same pressure as the fluid within the reservoir 14, operates on the greater area lower surface of the piston 72 and overcomes the force of the compressed air in the reservoir 14 acting on the upper effective surface of the piston 72 to provide an upwardly directed force that holds the resilient valve element 70 in engagement with the housing 12 to close the port 74 and holds the valve element 66 spaced from the valve seat 62 so that the passageway 20 normally communicates with the atmosphere through the opening or port 64 and exhaust passageway 24.

When the tool 10 is to be operated, a trigger or actuating element 98 pivotally mounted on the head portion 12a of the housing 12 by a pivot pin 100 is pivoted in a counterclockwise direction about the pin 100 to engage the lower end of the operating pin 84. This moves the pin 84 upwardly so that the O-ring 92 engages the adjacent portion of the valve body 80 to seal the passageway 94. In so moving, the O-ring 92 moves away from the member 86 so that the upper end of a groove 102 lying adjacent the pin 84 is uncovered. This permits the compressed air within the lower portion of the cylinder 78 to be discharged to the atmosphere through the passageway 96, the chamber 88, and the groove 102. When the compressed air is discharged from within the lower end of the cylinder 78, the compressed air acting on the effective upper surface of the piston 72 moves this piston and the connected valve stem 68 downwardly. In moving downnosepiece assembly 34.

swans wardly, the O-ring 66 moves into engagement with the tapered wall on the valve seat 62 to close the exhaust port or opening 64. This also moves the upper surface of the resilient valve element 7 out of engagement with the housing 12 to open the port or passageway 74. The passageway 26 and the upper end of the cylinder 13 are now placed-in direct communication with the fluid in the reservoir 14 so that the piston 26 and the connected driver blade 23 are driven downwardly to engage and drive the fasteners!) supplied to the drive track 32 by the magazine assembly 36.

During this downward movement of the piston 26, the air disposed in the cylinder 18 below the lower end of the piston 26 is discharged into the cavity 16 through the openings 56, and some portion of this air is discharged directly to the atmosphere through the unsealed interfaces between the structures forming the housing 12 and the In tools 10 designed to drive smaller fasteners, such as staples, it has been determined that the air discharged through the openings 56 into the cavity and the air discharged directly to the atmosphere through the interfaces including those between the walls of the drive track 32 and the blade 28 is adequate to prevent any substantial damping or retarding or" the downward movement of the piston 26. However, in other applications in which larger fasteners, such as brads or nails, are to be driven intorelatively hard substances, the diameter of the cylinder 80 and, thus, the volume of the air swept by the moving piston 26 becomes substantial, and it is desirable to provide positive means for venting the lower end of the cylinder 18 directly to the atmosphere.

The exhaust valve assembly 33 provides means for connecting the cavity 16 directly to the atmosphere whenever the tool 10 is operated. The valve assembly 33 (FIG. 3) includes a valve member 110 that is 'sli-dably mounted within an opening or bore 112 formed in the head portion 12:: of the housing. The valve member 111 includes a piston portion 110:: carrying an O-ring 114 and having an upper surface that is placed in direct communication -with the passageway 21? through a passageway or port 116.

In its normal condition, a compression spring 118 disposed at its lower end within an opening 120* in a threaded member 122 closing the lower end of the bore 112 and at its upper end within an opening 124 in the valve body 1 14] biases the valve element 110 to a position blocking communication between a passageway 126 (FIGS. 1-6) that extends between the cavity 16 and the bore 112 and another passageway 128 (FIGS. 1 and '5) that extends between the bore 112 and the atmosphere.

When the tool 10 is operated by actuating the control valve assembly 22, this assembly compressed air from the reservoir 14 to the passageway 20. This compressed air passes through the opening or port 116 into the upper end of the bore 112 and acts on the upper surface of the piston portion 110a of the valve member 119 to move this member downwardly against the resilient bias of the compression spring 118 from the normal position illustrated in FIG. 3 to the operated position shown in FIG. 5. This operated :or lower position is determined by the engagement of the lower end of the valve member 111) with the upper edge of the threaded closure 1,22. In this position, a recessed or notched portion 1101') in the valve member 110 places the passageways 126 and 128 in direct communication through the bore 112 so that any air expelled from the lower end of the cylinder 18 into the cavity 16 can be discharged directly to the atmosphere. The exhaust valve assembly 38 remains in this condition until the control valve assembly 22 is released to connect the passageway 20 to the atmosphere. At this time, the com,- pression spring 118 moves the valve element 110 from the position shown in FIG. to the position shown in FIGS. 3 and 6 to close 0ft communication between the passageways 126 and 128. Thus, the cavity 16 is returned 6 to its normal condition in which it is sealed 011 from communication with the atmosphere.

The piston 26 is pneumatically restored to its normal position engaging the bumper 52 under the control of the piston return valve assembly 40 following the release of the control valve assembly 22 and after a fastener 30 has been driven by the driver blade 28. The piston return valve assembly 40 (FIGS. 4-6) includes a valve member 130 slidably disposed in a bore 132 in the head portion 12a of the housing 12. The bore is formed from the upper end of the head portion 12a, the upper portion of the bore is closed by a plug 134. The lower end or the bore is placed in communication with the cavity 16 through a passageway 136. The valve mem ber 13!) includes a tapered lower end or valve portion 1319a that is adapted to seat on a resilient O-ring 138 to close off communication between the passageway 136 and a passageway 140 (FIGS. 1 and 4) that extends directly into the reservoir 14. The portion of the valve member 131 whose outer wall engages the wall of the bore or cylinder 132 provides a piston portion sealed with the Wall of the bore 132 by a resilient O-ring 142.

In the normal condition of the tool 16, the piston return valve assembly 40 is in a closed condition (FIGS. 4 and 5) preventing communication between the reservoir 14 and the cavity 16. To accomplish this, the compressed air continuously supplied to the lower end of the bore 132 through the passageway 14%} passes through a radially extending passageway 144 and a vertically extending bore or passageway 146 in the valve member 130 to be discharged into the bore 132 between the upper surface of the piston portion of the valve element 130 and the lower surface of the plug 134. A passageway 148 in the housing 12 and an aligned passageway 151 in the flanged portion 18a of the cylinder 18 are normally sealed by the O-rings 58 and 60 which are disposed on opposite sides of the port terminating the passageway 15% when the piston 25 is in its normal position. Thus, the compressed air supplied through the passageway 146 accumulates in the cavity between the lower surface of the plug 134 and the upper surface of the piston portion of the valve element 130 to provide a downwardly directed force that exceeds the upwardly directed force due to the compressed air acting on the lower surface of the piston portion. This downwardly directed force seats the valve portion 130a of the valve member 130 on the O-ring 138 to close off communication through the lower end of the bore 132 between the passageways 136; and 140. Thus, the compressed air from the reservoir 14 I cannot be supplied to the cavity 16 in the normal condition of the tool 1t),

When the tool 18 is operated by actuating the control valve assembly 22, compressed air is admitted to the passageway 241 in the manner described above so that the exhaust valve assembly 38 connects the cavity 16 .to the atmosphere and the piston 26 is driven downwardly to drive and set a fastener 30, When the piston 26 moves downwardly, the port terminating the passageway 150 is no longer sealed by the O-rings 58 and60 on the piston 26, and the compressed air or fluid supplied to the upper end ofthe cylinder 18'passes through the pas, sagewa ys 150 and 148 to accumulate in the bore 132 above the upper surface of the piston portion of the valve member 139. This compressed air supplements that supplied through the axial bore 146 so that the valve element 13% remains biased into engagement with the O-ring 138 during the interval in which the piston 25 is being driven. During and at the end of the driving stroke the exhaust valve assembly 38 and the piston return Valve assembly 40 are in the position shown in FIG. 5.

When the control valve assembly 22 is released so that the passageway 21 is connected to the atmosphere through the exhaust passageway 24, the exhaust valve assembly 38 is restored to the normal position shown in FIGLG to seal the cavity 16 from communication with the atmosphere. At this time, the upper portion of the in terior of the cylinder 18 disposed above the upper surface of the piston 28 is also connected to the atmosphere through the passageways 20 and 24. This permits the compressed air acting on the upper surface of the: valve element 130 to be discharged to the atmosphere. Since the passageways 148 and 150 have a greater air conveying capacity than the somewhat restricted radial or bleeder passageway 144, the compressed air in the upper end of the cylinder 132 is dissipated through the: passageways 148 and 150 faster than it can be replaced through the bleeder passageway 144. Thus, the upper surface of the piston portion of the valve member 130 is placed near atmospheric pressure.

The compressed air supplied by the passageway 140, which acts on the lower surface of the piston portionof the valve element 130, develops an upwardly directed component of force that shifts the valve member 130 from the normal position illustrated in FIG. to the displaced or operated position illustrated in FIG. 6 to move the tapered valve portion 130a out of engagement with the O-ring 133. This places the passageway 140 in communication with the passageway 136 through the lower end of the bore 132 and supplies Compressed air directly from the reservoir 14 to the cavity 16. This: compressed air fiows into the lower end of the cylinder 18 through the openings 56 (FIG. 2) and elevates the piston 26 to the normal position shown in FIGS. 2, 3, and 4. As the piston 26 moves to this position, the 0- rings 58 and 60 are carried on the piston 26 seal the passageway 150 from communication with the interior of the cylinder 18. Thus, the compressed air supplied through the bleeder passageway 144 and the axial bore 146 builds up in the cavity above the upper surface of the piston portion of the valve member 130. Although the upper and lower areas on the valve 130 are substantially equal when this valve is open, the air acting on the lower surface has a lower pressure because of the large volume of the connected chamber 16. This produces a net downwardly directed force.

At this time, the downward directed force moves the valve member 130 from the position shown in FIG. 6 to the position shown in FIG. 4 in which the tapered valve portion 130a again seats on the resilient O-ring 138. This closes off communication between the cavity 16 and the reservoir 14. Since the exhaust valve assembly 38 is closed, the compressed air in the cavity 16 and the lower portion of the cylinder 18 tends to hold the piston 26 and the driver blade 28 in the normal position shown in FIGS. 2-4. As indicated above, the lower end of the cylinder 18 is not sealed from the atmosphere, and this air can escape to the atmosphere so that the piston 26 is no longer pneumatically held in its retracted position engaging the bumper 52. However, the resilient engagement of the O-rings 58 and 60 with the inner wall of the cylinder 18 holds the piston 26 and the driver blade 28 in their normal positions even when the compressed air has been discharged from the lower end of the cylinder 18. If, for any reason, the piston 26 drops below its normal position the port terminating the passageway 150 is again connected to the atmosphere through the passageways 20 and 24, and the valve member 130 is again operated to supply an additional quantity of air from the reservoir 14 to the lower end of the cylinder 18 to return the piston 26 and the driver blade 28 to their normal positions.

A fastener driving tool indicated generally as 200 and forming a second embodiment of the invention is illustrated in FIGS. 7 and 8 of the drawings. The tool 200 is similar to the tool illustrated in FIGS. l6 but includes a common pneumatic operating means for the valve assemblies controlling the connection of the lower end of the drive cylinder to the source of pressure fluid and the atmosphere. The tool 200 also does not utilize a cavity communicating with the lower end of the drive cylinder.

Referring now more specifically to FIGS. 7 and 8 of the drawings, the tool 200 includes a housing 202 having :a generally vertically extending head portion 202a forming a cylinder 204 and a rearwardly extending handle portion 202E; providing a reservoir 206 that is adapted to be supplied with a pressurized fluid, such as compressed air. The open upper end of the cylinder 204 is connected to a manually actuated control valve assembly indicated generally at 208 by a rearwardly extending passageway 210 in the housing. The control valve assembly 208, which is substantially identical to the control valve assembly 22, normally connects the passageway 210 to an exhaust passageway 212 in the handle portion 202:) and, when operated, interrupts the connection between the passageways 210 and 212 and connects the open upper end of the cylinder 204 to the reservoir 206 over the passageway 210.

When compressed air is connected to the passageway 210 by the control valve assembly 208, a piston 214 which normally engages a resilient bumper 216 carried on a closure 218 for the open upper end of the head portion 202a of the housing 202 and which carries a pair of sealing O-rings 220 and 222 is driven downwardly so that a connected driver blade 224 engages and drives a fastener supplied to a drive track in a nosepiece assembly 226 by a magazine assembly indicated generally as 228. The termination of the downward movement of the piston 214 is cushioned by an annular resilient bumper 230 which is disposed within the lower end of the cylinder 204 to surround a guide member 232 through which the driver blade 224 extends, the lower end of the piston 214 being recessed to accommodate the upwardly projecting portion of the member 232.

The lower end of the cylinder 204 is selectively connected to either the atmosphere or to the compressed fluid in the reservoir 206 under the control of a combined exhaust and piston return valve assembly indicated generally as 234. The assembly 234 includes a valve element 236 slidably mounted in three concentric and axially aligned openings or bores 238, 240, and 242 formed in the housing 202. These bores can be formed from the top of the housing 202 through an opening 244 therein that is closed by a threaded plug 246, a threaded plug 248 closing off communication between the cylinder or bore 238 and the passageway 210.

To control the selective connection of the lower end of the cylinder 204 to the atmosphere, the bore 242 is placed in communication with the lower end of the cylinder 204 through a passageway 250, and the bore 242 is placed in communication with the atmosphere through a passageway 252. The valve member 236 includes a lower valve portion 236a which normally occupies the position within the opening 242 illustrated in FIG. 7 and which can be moved upwardly to the position illustrated in FIG. 8 to close off communication between the lower end of the cylinder 204 and the atmosphere through the passageways 259 and 252 and the bore 242.

To provide means for selectively supplying compressed air from the reservoir 206 to the lower end of the cylinder 204, the reservoir 206 is placed in communication with an intermediate portion of the cylinder or bore 240 by a passageway 254. In the normal condition of a valve assembly 234, a tapered valve portion 23Gb on the valve member 236 engages a resilient O-ring 256 mounted on the shoulder formed at the junction of the bores 240 and 242 to close oif communication between these chambers and thus prevent the fiow of compressed air from the passageway 254 through the cylinders 240 and 242 to the passageway 250.

To provide means for pneumatically operating the valve assembly 234, the upper end of the valve element 236 is provided with a piston portion 2360 sealed by two O-rings 258 and 260 that slidably engage the walls of .and set a fastener or staple.

9 the cylinders 238 and 240, respectively. The volume at the lower end of the cylinder 238 bounded by the O-rings 253 and 260 is continuously connected to the atmosphere by a passageway (not shown). The compressed air continuously supplied from the reservoir 206 through passageway 254 passes through a bleeder port or passageway 262 to an axially extending opening 264 in the upper end of the valve element 236. This air is discharged into the upper end of the cylinder 238 and I also passes into a passageway 266 that extends between the upper end of the cylinder 238 and the wall of the cylinder 204 in a position disposed between the O-rings 220 and 222 on the piston 214 when this piston is in its normal position. The compressed air supplied through the passageways 262 and 264 acts on the greater upper surface of the piston portion 2360 to provide a downwardly directed force that is greater than the upwardly directed force resulting from the compressed air supplied by the passageway 254 acting on the smaller lower surface of the piston portion 2360. This downwardly directed force seats the tapered valve portion 23617 on the O-ring 256 to close off communication between the bores 240 and 242 and also holds the vvalve portion 236a in a position in which the passageways 250 and 252 are in communication through the cylinder 242.

As set forth above, the tool 200 is operated by actuating the control valve assembly 208 to disconnect the passageway 210 from the exhaust passageway 212 and to connect this passageway to the reservoir 206. This provides a flow of compressed air through the passageway 210 into the cylinder 204 that drives the piston 214 and the connected driver blade 22-4 downwardly to engage During this downward movement, the valve assembly 234 permits the air disposed below the piston 214 to be discharged to the atmosphere through the passageways 250 and 252 and the cylindrical opening or bore 242. When the piston 214 moves downwardly so that the O-rings 220 and 222 no longer seal the passageway 266, compressed air from the interior of the cylinder 204 also flows through the passageway 265 to supplement the air supplied by the passageway 264. This merely insures that the central valve assembly 234 remains in its normal position. However, when the control valve assembly 208 is released to connect the passageway 210 to the exhaust passageway 212 and to close elf communication between the passageway 210 and the reservoir 206, the portion of the cylinder 204 disposed above the piston 214 is also connected to the atmosphere. The compressed air in the upper end of the cylinder 233 .is now discharged to the atmosphere through the passageway 266 and at a faster rate than it can be supplied through the bleeder passageway 262. The upper end or" the cylinder 238 now drops to near atmospheric pressure.

With the upper efiective surface of the piston portion 236a placed at atmosphericipressure, the compressed air supplied by the passageway 254 acting on the lower effectivesurface of the piston portion 236a produces an upwardly directed component of force that shifts the valve element 236 upwardly from the position shown in FIG. 7 to the operated position shown in FIG. 8. movement of the valve element 236 moves the valve portion 236a to a position in which communication between the bore 242 and the. passageway 252 is closed and thereby seals the lower end of the cylinder 204 from communication with' the atmosphere. This same movement of the valve 236 moves the tapered valve portion 236k out of engagement with the O-ring 256 so that the bores 240 and 242 are now placed in communication. This permits compressed air from the reservoir 206 to flow through the passageway 254, the bores 240 and 242, and the passageway 250 into the lower end of the cylinder 204. Since the upper portion of the cylinder 204 is connected to the atmosphere through the passageways 210 and 222, this compressed air moves the piston 214 and the connected it? driver blade 224 upwardly until the upper surface of the piston 2'14 engages the resilient bumper 216.

When the piston 214 moves from the displaced position illustrated in FIG. 8 to the normal position shown in FIG. 7, the O-rings 220 and 222 prevent communication between the interior of the cylinder 204 and the passageway 266. Thus, the compressed air supplied through the bleeder port 262 and the passageway 264 accumulates in the upper end of the chamber 238 until such time as the downwardly directed force exceeds the upwardly directed 'force due to the compressed air acting on the lower surface of the piston portion 2360. At this time, the valve element 236 moves downwardly from the position illustrated in FIG. 8 to the position illustrated in FIG. 7 so that the tapered valve portion 23612 engages the O-ring 256 to prevent an additional flow of compressed air from the reservoir 206 into the lower end of the cylinder 204. This movement of the valve element 236 also moves the valve portion 236a out of alignment with the inner port terminating the passageway 252 so that compressed air contained in the lower end of the cylinder 204 is being exhausted to the atmosphere through the passageways .250 and 252. The piston 214 does not drop from its normal position at this time inasmuch as the resilient engagement of the O-rings 220 and 222 with the wall surface of the cylinder 204 prevents downward movement of the piston 214. If, however, the piston 214 drops from its normal position for any reason, the passageway 266 is again connected to the atmosphere, and the valve assembly 234 is operated in the manner described above to close the exhaust connection for the lower end of the cylinder 294 and to supply compressed air thereto for returning the piston 214 and the driver blade 224 to their normal positions.

The novel pneumatic piston neturn means embodied in the tools 10 and 200 are so arranged that the overall height of these tools remains at a minimum determined by the length of the driving stroke required for the driver blades 28 and 224 and, in providing means for receiving the air disposed below the pistons 26 and'214 during their driving strokes, insure that the maximum driving power commensurate with the diameter of the pistons is obtained during the driving strokes. The air swept out of the cylinders 18 and 204 during the power strokes and the compressed air positively supplied to the lower end of these cylinders during the piston return strokes avoids any ingestion of dirt or other material into the lower end of the cylinders that might interfere wtih the proper movement of the pistons. This problem is presented in a number of prior pneumatic return systems in which the upward or return movement of the piston produces an inwardly directed flow of air from the atmosphere into the lower end of the cylinder that carrier with it lint or dirt particles that accumulate in the cylinder. .In addition, the pistons 26 and 214 are always supplied with as much compressed air from the reservoirs 14 and 20.6 as is necessary to eliect full and complete return of these pistons to their normal positions. In many prior pneumatic return systems, the quantity of air used for piston return is fixed so that the pistons in these constructions cannot be fully returned to their normal position if sliding movement of the piston is impeded by foreign matter ingested int-o the cylinder or if the driver blade becomes slightly canted in the drive track.

Although the present invention has been described with reference to two illustrative embodiments thereof, it

' should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1.'A fastener driving tool comprising a housing including a cylinder and a reservoir supplied with fluid under pressure, fastener driving means including a piston slidably mounted in the cylinder, first valve means carried on the housing and operable from a normal position connecting one end of the cylinder to the atmosphere to an operated position connecting the one end of the cylinder to the reservoir, second valve means carried on the housing and operable from a normal position connecting the other end of the cylinder to the atmosphere to an operated position connecting the other end of the cylinder to the reservoir, and means responsive to the fluid pressure in the one end of the cylinder for selectively operating the second valve means between its normal and operated positions.

2. A fastener driving tool for use with a source of pressure fluid comprising a housing including both a cylinder having an open end and a reservoir continuously supplied with fluid from the source, fastener driving means including a piston slidable in the cylinder, con trol means for selectively connecting the open end of the cylinder to the atmosphere and to the reservoir to drive the piston from a normal position to a displaced position, a passageway communicating with the opposite end of the cylinder, valve means normally connecting the passageway to the atmosphere and operable to connect the passageway to the reservoir, and means communicating with the cylinder through a port closed by the piston in its normal position for operating said valve means in response to the connection of said port to the atmosphere.

3. A fastener driving tool for use with a source of pressure fluid comprising a housing having a cylinder and a reservoir, fastener driving means including a piston slidably mounted in the cylinder, said housing having a passageway connecting an open end of the cylinder to a first port communicating with the atmosphere and a second port communicating with the reservoir, first valve means for alternatively opening the first and Second ports to selectively supply fluid from the reservoir to drive the piston, first fluid conveying means in the housing between the other end of the cylinder and the reservoir to supply fluid to the cylinder below the piston to return the piston to a position adjacent the open end of the cylinder, first fluid operated valve means for controlling the flow of fluid through the first fluid conveying means and including a port opening into the cylinder adjacent its open end, second fluid conveying means connecting the other end of the cylinder with the atmosphere, and second fluid operated valve means for controlling the second fluid conveying means and including means communicating with the passageway.

4. A fastener driving tool for use with a source of pressure fluid comprising a housing including both a cylinder having an open end and a reservoir continuously supplied with fluid from the source, fastener driving means including a piston slidable in the cylinder, control means for selectively connecting the open end of the cylinder to the atmosphere and to the reservoir to drive the piston from a normal position to a displaced position, a passageway communicating with the opposite end of the cylinder, first valve means normally connecting the passageway to the atmosphere, second valve means for connecting the passageway to the reservoir, said second valve means being normally closed, and fluid operated means responsive to the pressure in the open end of the cylinder for concurrently operating the first and second valve means.

5. The fastener driving tool set forth in claim 4 in which the fluid operated means includes a cylinder means in the housing, piston means connected to the first and second valve means, and means placing second cylin- .der means in communication with the cylinder adjacent the open end thereof.

6. A fastener driving tool comprising a housing hav- .ing a vertically extending head portion containing a cylinder open at its top and a hollow handle extending rearwardly from the head portion and providing a reservoir of fluid under pressure, fluid conveying means extending rearwardly from the open end of the cylinder and having a first port communicating with the reservoir and a second port communicating with the atmosphere, first valve means carried on the housing and operable between a first position in which the first port is closed and the second port is open and a second position in which the first port is open and the second port is closed, fastener driving means including a piston slidably mounted in the cylinder, said first valve means operating to supply fluid to the open end of the cylinder to drive the piston to a displaced position and to exhaust fluid from the open end of the cylinder to permit the piston to be returned from the displaced position to a normal position, second valve means for selectively supplying fluid from the reservoir to the other end of the cylinder to return the piston from the displaced position to the normal position, and means controlled by the presence or absence of fluid in the open end of the cylinder for operating the second valve means.

7. A fastener driving tool comprising a housing having a vertically extending head portion containing a cylinder open at its top and a hollow handle extending rearwardly from the head portion and providing a reservoir of fluid under pressure, fluid conveying means extending rearwardly from the open end of the cylinder and having a first port communicating with the reservoir and a second port communicating with the atmosphere, first valve means carried on the housing and operable between a first position in which the first port is closed and the second port is open and a second position in which the first port is open and the second port is closed, fastener driving means including a piston slidably mounted in the cylinder, said first valve means operating to supply fluid to the open end of the cylinder to drive the piston to a displaced position and to exhaust fluid from the open end of the cylinder to permit the piston to be returned from the displaced position to a normal position, second valve means for selectively supplying fluid from the reservoir to the other end of the cylinder to return the piston from the displaced position to the normal position, third valve means for selectively connecting the other end of the cylinder to the atmosphere, and means responsive to the fluid pressure at the open end of the cylinder for selectively operating the second and third valve means.

8. A fastener driving tool comprising a housing having a vertically extending head portion containing a cylinder open at its top and a hollow handle extending rearwardly from the head portion and providing a reservoir of fluid under pressure, fluid conveying means extending rearwardly from the open end of the cylinder and having a first port communicating with the reservoir and a second port communicating with the atmosphere, first valve means carried on the housing and operable between a first position in which the first port is closed and the second port is open and a second position in which the first port is open and the second port is closed, fastener driving means including a piston slidable mounted in the cylinder, said first valve means operating to supply fluid to the open end of the cylinder to drive the piston to a displaced position and to exhaust fluid from the open end of the cylinder to permit the piston to be returned from the displaced position to a normal position, second valve means for selectively supplying fluid from the reservoir to the other end of the cylinder to return the piston from the displaced position to the normal position, third valve means for selectively connecting the other end of the cylinder to the atmosphere, means responsive to the fluid pressure at the open end of the cylinder for controlling the operation of the second valve means, and means responsive to the fluid pressure in the passageway for controlling the operation of the third valve means.

9. A fastener driving tool for use with a source of pressure fluid comprising a housing having both a generalliy vertical head portion and a hollow handle portion extending rearwardly from the head portion, said head portion having a cylinder with an open upper end and a cavity communicating with the lower end of the cylinder, said hollow handle portion providing a reservoir of fluid, said housing also having a passageway communicating with the open end of the cylinder and having a first port exposed to the atmosphere and a second port exposed to the fluid in the reservoir, first valve means normally closing the second port and opening the first port and operable to close the first port and open the second port, fastener driving means including a piston slidable in the cylinder and operable from a normal position adjacent the open end of the cylinder when the second port is opened to a displaced position adjacent the other end of the cylinder, movement of the piston from its normal position to its displaced position forcing the fluid below the piston into the cavity, said housing having a bore with one fluid conveying means connecting the bore to the cavity and a second fluid conveying means connecting the bore with the reservoir, second valve means movably mounted in Said bore and normally operative to prevent communication through the bore between the first and second fluid conveying means, and means for moving said second valve means to a position placing the first and second fluid conveying means in communication through the bore in response to the connection of the passageway to the atmosphere through said first port.

10. A fastener driving tool for use with a source of pressure fluid comprising a housing having both a generally vertical head portion and a hollow handle portion extending rearwardly from the head portion, said head portion having a cylinder with an open upper end and a cavity communicating with the lower end of the cylinder, said hollow handle portion providing a reservoir of fluid, said housing also having a passageway communicating with the open end of the cylinder and having a first port exposed to the atmosphere and a second port exposed to the fluid in the reservoir, first valve means normally closing the second port and opening the first port and operable to close the first port and open the second port, fastener driving means including a piston slidable in the cylinder and operable from a normal position adjacent the open end of the cylinder when the second port is opened to a displaced position adjacent the other end of the cylinder, movement of the piston from its normal position to its displaced position forcing the fluid below the piston into the cavity, fluid conveying means extending between the cavity and the reservoir, second valve means controlling the flow of fluid through the fluid conveying means from the reservoir to the cavity to provide a body of fluid for moving the piston from its displaced position to its normal position, pneumatic means slidably mounted on the housing for controlling operation of the second valve means, and means controlled by the first valve means for selectively connecting the pneumatic means to the atmosphere and supplying fluid from the reservoir.

References Cited in the file of this patent UNITED STATES PATENTS 1,354,348 Smith Sept. 28, 1920 1,494,030 Slater May 13, 1924 2,989,948 Forrester June 27, 1961 

1. A FASTENER DRIVING TOOL COMPRISING A HOUSING INCLUDING A CYLINDER AND A RESERVOIR SUPPLIED WITH FLUID UNDER PRESSURE, FASTENER DRIVING MEANS INCLUDING A PISTON SLIDABLY MOUNTED IN THE CYLINDER, FIRST VALVE MEANS CARRIED ON THE HOUSING AND OPERABLE FROM A NORMAL POSITION CONNECTING ONE END OF THE CYLINDER TO THE ATMOSPHERE TO AN OPERATING POSITION CONNECTING THE ONE END OF THE CYLINDER TO THE RESERVOIR, SECOND VALVE MEANS CAR- 